Method of constructing electrical apparatus

ABSTRACT

A METHOD OF CONSTRUCTING ELECTRICAL APPARATUS HAVING A GAPPED MAGNETIC CORE STRUCTURE COMPRISING UPPER AND LOWER YOKE PORTIONS, FIRST AND SECOND OUTER LEG MEMBERS, AND A GAPPED INNER WINDING LEG, USING SIMILARLY DIMENSIONED FSHAPED LAMINATIONS. FOUR F-SHAPED LAMINATIONS, TWO OF WHICH ARE REVERSED, ARE ASSEMBLED TO PROVIDE A BASIC GROUP OF LAMINATIONS, AND A PLURALITY OF BASIC GROUPS ARE SUPERPOSED TO PROVIDE A PRELIMINARY RECTANGULAR STRUCTURE OF FRAME IN WHICH THE LENGTH OF THE OUTER LEGS IS ALMOST TWICE THEIR DIMENSION IN THE FINAL CORE STRUCTURE, WHICH PROVIDES AN INNER LEG HAVING A GAP THEREIN SUFFICIENT TO RECEIVE AN ASSOCIATED ELECTRICAL WINDING. THE PRELIMINARY STRUCTURE IS THEN COMPRESSED TO ITS FINAL DIMENSIONS TO CAUSE THE INNER WINDING LEG PORTIONS TO ADVANCE INTO THE ELECTRICAL WINDING AND PROVIDE A NON-MAGNETIC GAP THEREIN.

United States Patent 1191 Caputo et al.

[ June 28, 1974 METHOD OF CONSTRUCTING Primary Examiner-Charles W.Lanham ELECTRICAL APPARATUS Assistant Eraminer-Carl E. Hall [75]Inventors: William R. Caputo, Wycoff; Clyde Attorney Agent or firm-DLackey M. Mullls, Glen Rock, both of NJ. [57] ABSTRACT Assigns-e1Westinghouse Electric Corporation, A method of constructing electricalapparatus having Plttsburgh, a gapped magnetic core structure comprisingupper [22] Filed; May 17 1973 and lower yoke portions, first and secondouter leg members, and a gapped inner winding leg, using simi- 7 1 PP361,088 larly d1mens1oned F-shaped laminatlons. Four F- shapedlaminations, two of which are reversed, are as- 52 us. 01 29/606, 29/609336/165 sembled to Provide a basic group of laminations and 8 33 /17336/217 336/234 hour/W0 plurality Of basic groups are superposed toprovide a 5 Fi f Search n 29/ 0 09- 33 /134 1 5 preliminary rectangularstructure Of frame in which 336/178 212 217 the length of the outer legsis almost twice their dimension in the final core structure, whichprovides an [56] References Cited inner leg having a gap thereinsufficient to receive an associated electrical winding. The preliminarystruc- UNITED STATES PATENTS ture is then compressed to its finaldimensions to 1,726,100 8/1929 Daqosta 29/606 X cause the inner windingleg portions to advance i 29/609 UX the electrical winding and provide anon-magnetic gap 355,689 lI/l967 Paddison er al. 336/234 therem' 9Claims, 6 Drawing Figures I O O O O O 56 o o ./54 0 O O Q n 6 68\- T O O64 .188 o 2 a O O O O O METHOD OF CONSTRUCTING ELECTRICAL APPARATUSBACKGROUND OF THE INVENTION 1. Field of the Invention The inventionrelates in general to electrical inductive apparatus, and morespecifically to electrical inductive apparatus having a gapped magneticcore structure, such as an electrical reactor.

2. Description of the Prior Art Certain types of electrical inductiveapparatus, such as iron core reactors, utilize a magnetic core structurehaving one or more non-magnetic gaps in the magnetic circuit to providepredetermined electrical characteristics. The gapped magnetic corestructure produces sound levels which may be objectionable in certainapplications. In a specific application for an air cooled iron corereactor, magnetic cores were constructed using both the C and E-I coreconfigurations. Both core arrangements produced a sound level ofapproximately 90 db well above the maximum acceptable 70 db level (at 4feet) for this specific application. The mating faces of the Come, andthe mating faces of the E-I core were ground and cemented together withan epoxy resin. This lowered their sound levels to an acceptablemagnitude. Shipment of the reactors, however, deleteriously affected theflatness of the mating faces and the reactors had to be disassembled andtheir mating faces reground in order to again provide an acceptablesound level.

Gapped magnetic core assemblies may be formed by stacking flat F-shapedlaminations, such as disclosed in U.S. Pat. No. 3,355,689. Thisarrangement eliminates the grinding and cementing operations, sincethere are no mating faces, and this arrangement is thus preferable tothe C and BI arrangements. Thus, it would be desirable to provide a newand improved method of constructing gapped electrical inductiveapparatus using F-shaped laminations, which method facilitates theassembly of the apparatus while achieving a sound level of 70 db. orless.

SUMMARY OF THE INVENTION Briefly, the present invention is a new andimproved method of constructing electrical inductive apparatus having agapped magnetic core structure. The major non-magnetic gap of theapparatus is disposed within the associated winding such that it islocated at substantially the midpoint thereof, which location ispreferable when the reactor is used as part of a filter network forreducing the ripple magnitude of the A-C component in direct current.This location of the gap, however, does not adversely affect the soundlevel of the apparatus, nor does it complicate the manufacture of theapparatus, due to a new and improved method of constructing theapparatus.

More specifically, the magnetic core is constructed of similarly shapedand dimensioned, flat, F-shaped metallic, magnetic laminations, with thedimensions of the back portion and projecting portions of thelaminations and the dimensions of the associated winding, all beingselected to enable a preliminary rectangular structure or frame havingtwo yoke portions, two outer leg portions, and an intermediate orwinding leg to be built up which enables the laminations which make upeach of the two portions of the gapped winding leg to be rigidly clampedtogether before they are disposed within the winding. The yoke portionsof this preliminary structure are spaced far enough apart to enableandthe yoke portions are moved towards one another to advance the ends ofthe winding leg portions into the opening of the winding to establishthe desired non magnetic gap therein. The laminations are dimensionedsuch that when the desired gap in the winding leg is established, theends of the laminations which make up the outer leg members are spacedfrom the back portions of the other F-shaped lamination in the samelayer, to insure that there are no mating faces to produce-noise whenthe apparatus is energized.

BRIEF DESCRIPTION OF THE DRAWINGS The invention may be betterunderstood, and further advantages and uses thereof more readilyapparent, when considered in view of the following detailed descriptionof exemplary embodiments, taken with the accompanying drawings, inwhich:

FIG. 1 is a perspective view of electrical inductive apparatus which maybe constructed according to the teachings of the invention; and

FIGS. 2 through 6 illustrate the steps of constructing the electricalinductive apparatus shown in FIG. 1, according to the teachings of theinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to the drawings, andFIG. 1 in particular, there is shown electrical inductive apparatus 10,such as an electrical reactor, having an electrical winding 12, shown inphantom, disposed in inductive relation with a magnetic core 14.Magnetic core 14 includes a plurality of layers 15 of metalliclaminations assembled to provide first and second yoke portions 16 and18, respectively, first and second outer leg portions 20 and 22,respectively, which extend between the spaced first and second yokeportions 16v and 18, and an intermediate or winding leg member 24 whichhas a non-magnetic gap 26 therein. The winding is disposed about thewinding leg 24, with winding leg 24 having a first portion 28 extendingoutwardly from yoke 16, and a second portion 30 extending outwardly fromyoke 18. The first and second portions 28 and 30, respectively, of thewinding leg are aligned with one another.

A plurality of lock plate members 32, 34, 36, 38, 40 and 42 are disposedagainst the flat major surfaces on one side of the magnetic core 14, andsimilar lock plate members are disposed on the other side thereof. Nutand bolt combinations, such as nut and bolt combination 44, are disposedto clamp the laminations rigidly together, perpendicular to their fiatmajor surfaces. The bolts are disposed through aligned openings in theface plates and laminations, which openings have insulating sleevemembers disposed therein to prevent the bolt from shorting adjacentlaminations. Insulating washers are also used to prevent shorted turns.Mounting feet (not shown) may be bolted to the lower yoke portion 18.

Electrical apparatus may be advantageously constructed according to theteachings of the invention, with the steps of the new and improvedmethod being shown in FIGS. 2 through 6.

More specifically, as illustrated in FIG. 2, the first step of theinvention is to provide a first F-shaped lamination 50 formed frommagnetic material, such as silicon steel, having a thickness dictated bythe specific application. Lamination 50 has a back portion 52, and firstand second projecting portions 54 and 56, respectively, which projectoutwardly from a common edge of the back portion. The first projectingportion 54 is located at one end of the back portion 52, forming anouter corner 58 at their intersection. The second projecting portion 56is disposed to extend outwardly from substantially the midpoint of theback portion 52, represented by center line 60. Since the secondprojeeting portion 56 will function as the winding leg, it will carrytwice the magnetic flux as the yoke and outer leg portions and thus thewidth dimension of the second projecting portion 56 is preferably twicethe width W of the yoke and outer leg portions. The back portion 52 andfirst and second projecting portions 54 and 56 each have a plurality ofopenings disposed therein, perpendicular to their major opposedsurfaces, such as opening 62, for aligning and clamping superposedlaminations with clamping means, such as the nut and bolt combination 44shown in FIG. 1.

The next step of the method, illustrated in FIG. 3, is to provide asecond F-shaped lamination 64, which is similar in configuration anddimensions to lamination 50. Lamination 64 includes a back portion 66,first and second projecting portions 68 and 70, respectively, and anouter corner 72 formed by the intersecting back and first projectingportions. The second F-shaped lamination 64 is disposed in the sameplane as the first F- shaped lamination, with the outwardly extendingends of. their second projecting portions 56 and 70 facing one anotherand aligned with one another, as indicated by dotted lines 74. Thefacing ends of the second projecting portions 56 and 70 are spaced apartby a dimension indicated by a line 76, which-exceeds the dimension ofthe associated electrical winding 12 between the ends of the windingwhich have the openings therein for receiving the winding leg of themagnetic core. The winding, and first and second projecting portions,are all dimensioned such that when the second projecting portions 56 and70 are spaced by a dimension 76 sufficient to receive the winding 12,that the ends of the first projecting portions extend past one anotherby a dimension 78. The magnitude of dimension 78 is not critical, itonly being important that they overlap. It will be noted that both thefirst and second F-shaped laminations are oriented with similar sidesthereof facing upwardly, such that corner 58 provides the upperrighthand corner and comer 72 provides the lower left-hand corner, of apreliminary structure or frame which is completed in FIG. 3 by dottedlines 80 and 82.

The next step, shown in FIG. 4, is to provide a third F-shapedlamination 84, similar in configuration and dimensions to the first andsecond F-shaped laminations 50 and 64, except that it is turned over orinverted. Lamination 84 has a back portion 86, first and secondprojecting portions 88 and 90, and an outer corner 92 formed by theintersection of the back and first projecting portions 86 and 88.Lamination 84 is stacked such that its outer comer 92 forms the lowerright-hand comer of the preliminary structure, with its back portion 86superposed over the back portion 66 of lamination 64, its secondprojecting portion superposed over the second projecting portion 70 oflamination 64, and its first projecting portion extending towards andoverlapping the end of the first projecting portion of lamination 50 bythe dimension 78.

The next step, shown in FIG. 5, is to provide a fourth F-shapedlamination 94 similar in configuration and dimensions to the first,second and third F -shaped laminations, and inverted, relative to theorientation of the first and second F-shaped laminations, similar to thethird F-shaped lamination 84. Lamination 94 has a back portion 96, firstand second projecting portions 98 and 100, and an outer corner 102formed by the intersection of the back and first projecting portions 96and 98, respectively. Lamination 94 is stacked such that its outercorner 102 forms the upper left-hand corner of the preliminarystructure, with its back portion 96 superposed over the back portion 52of the first lamination 50, its second projecting portion 100 superposedover the second projecting portion 56 of the first lamination, and itsfirst projecting portion extending towards and overlapping the end ofthe first projecting portion of lamination 64, by the dimension 78.

The four laminations 50, 64, 84 and 94 form a basic group oflaminations, providing a closed rectangular preliminary structure, uponwhich the desired number of additional basic groups of laminations arestacked to provide the desired build dimension 104, as illustrated inFIG. 1. The back portions of the first and fourth laminations providethe yoke 16, the back portions of the second and third laminationsprovide the yoke 18, the first projecting portions of the second andfourth laminations provide outer leg 20, the first projecting portionsof the first and third laminations provide outer leg 22, the secondprojecting portions of the first and fourth laminations provide portion28 of winding leg 24, and the second projecting portions of the secondand third laminations provide portion 30 of the winding leg 24. It willbe noted that the longitudinal dimension of the outer leg portions ofthe preliminary structure is almost twice the dimension that these legswill have in the final configuration of the magnetic core.

While the basic group of laminations includes four similar butdifferently oriented laminations to provide the four outer corners ofthe preliminary core structure, it is to be understood that eachlamination may represent two, three or more laminations, whichfacilitates the handling and stacking thereof. For example, lamination50 shown in FIG. 1 may represent three superposed laminations, and theremaining laminations of the basic group introduced in FIGS. 3, 4 and 5,would also each represent three superposed laminations.

The next step, after providing the desired build dimension of thepreliminary magnetic core structure, which step is also illustrated inFIG. 5, is to rigidly clamp the superposed second projecting portions ofthe laminations together. This step, for example, may be accomplished bynut and bolt combinations. An insulating sleeve member (not shown) isinserted into each of the aligned openings in portions 28 and 30 of thewinding leg 24, insulating lock plate members 40 and 42 are disposedover the portions 28 and 30 of the winding leg, on the side shown inFIG. 5, as well as on the reverse side, and bolts are inserted throughthe sleeve members and tightened with nuts, such as the nut and boltcombination 44.

The next step, also illustrated in FIG. 5, is to dispose the electricalwinding 12 within the opening defined by the rectangular preliminarystructure, with the opening 112 in the winding 12 aligned with thefacing ends of the portions 28 and 30 of the winding leg 24. Winding 12may then be telescoped over one of these portions, such as portion 30,and the preliminary structure compressed by moving the yokes l6 and 18towards one another, to slide the interleaved portions of thelaminations which make up the outer legs over one another until thedesired non-magnetic gap 26 is achieved between the facing ends ofportions 28 and 30. The openings 62 in the outer leg portions will bealigned with one another when the proper gap dimension is achieved.

FIG. 6 illustrates the electrical inductive apparatus 10, after the stepof compressing the preliminary structure to provide the final dimensionsof the magnetic core. it will be noted that the step of closing thedimensions of the preliminary structure to the final dimensions of themagnetic core 14 stops before the ends of the first projecting portionsabut the back portions of the laminations in the same layer. This isimportant, in order to prevent any mating faces in the magnetic corestructure, to thus reduce the energized sound level of the apparatus,compared with a structure in which these faces are allowed to contactone another. The gaps between the ends of the first projecting portionand the back portions, such as the gap 114 shown in FIG. 6, add to themajor non-magnetic gap 26 and are taken into consideration when settingthe size of gap 26 to achieve the desired inductance versus currentcurve.

The final step, shown in FIG. 6, is to clamp the laminations rigidlytogether which make up the outer leg portions and the upper and loweryoke portions. This step may, for example, include the steps ofdisposing insulating sleeves in each of the aligned openings, placinginsulating lock plate members over the outer surfaces of thelaminations, disposing bolts through the sleeves, and tightening thesuperposed laminations with nuts disposed on the bolts. The apparatusused in the final step of clamping the yoke and outer leg portionstogether is most clearly shown in FIG. 1, which was hereinbeforedescribed.

In summary, there has been disclosed a new and improved method ofconstructing electrical inductive apparatus having a gapped magneticcore, which structure has no mating faces. Non-magnetic gaps areestablished in each layer of laminations of the magnetic core, which arerigidly held in place by frictional forces established by clampingmeans. The major nonmagnetic gap is disposed centrally within theelectrical winding, which is desirable because it provides the flattestinductance versus current curve. The method does not progressively buildup the laminations about the winding which would make it difficult torigidly clamp the lamination portions which extend into the opening ofthe winding. The magnetic core is constructed to first provide apreliminary structure which permits the lamination portions of thewinding leg to be rigidly clamped together, before they are disposedwithin the opening in the winding, and yet the magnetic core isassembled into its final dimensions without the necessity of trying tointerleave loose ends of laminations from two separate structures. Theinterleaving is started when the preliminary structure is stacked, andcompleted after the lamination portions of the winding leg are clampedwhile the winding leg portions are inserted into the opening of thewinding.

Electrical inductive apparatus constructed according to the teachings ofthe invention, using 0.025 inch thick laminations, and stacking threeF-shaped laminations at a time, was tested and found to operate with anenergized sound level below the required maximum of db for theapplication, and the sound level was not deleteriously affected byshipment, as there are no mating faces in the structure to be displacedby shipping stresses.

We claim as our invention: 1. A method constructing electrical apparatushaving a gapped magnetic core structure, comprising the steps of:

providing an electrical winding having first and second ends and anopening which extends between its ends, providing a plurality of flat,metallic F-shaped laminations, each of which has a back portion andfirst and second spaced parallel members which project outwardly fromthe back portion adjacent an end and midpoint thereof, respectively,providing a plurality of superposed groups of assembled F-shapedlaminations by placing first and second- F-shaped laminations in thesame plane with the end of their second members aligned and facing oneanotherbut spaced by a distance equal to or greater than the length ofthe electrical winding between its first and second ends, invertingthird and fourth ones of said F-shaped laminations, and stacking saidthird and fourth F-shaped laminations with their back portions andsecond members superposed on the back portions and second mem bers ofsaid first and second F-shaped laminations, respectively, with the endsof the first members of said third and fourth F -shaped laminationsoverlappingthe ends of the first members of said second and firstF-shaped laminations, respectively, placing said electrical windingbetween the facing ends of the second members of said F-shapedlaminations, with its opening aligned therewith,

and closing the spacing between the facing ends of the second members ofsaid F-shaped laminations to provide a winding leg within the opening ofsaid electrical winding having a predetermined nonmetallic gap therein.

2. The method of claim 1 wherein the step of closing the spacing betweenthe facing ends of the second members of said F-shaped laminationsincludes the step of sliding the overlapped ends of the first members ofthe F-shaped laminations relative to one another to provide a pluralityof layers which include alternate layers of only the first and secondF-shaped laminations, interleaved by layers which include only the thirdand fourth F-shaped laminations.

3. The method of claim 2 wherein the step of sliding the first membersof the F-shaped laminations is termi nated before the end of the firstmember of one F- shaped lamination abuts the back of the other F-shapedlamination in the same layer, to provide a non-metallic gaptherebetween.

4. The method of claim 3 including the step of clamping the superposedsecond members of the F-shaped laminations together, prior to the stepof closing the spacing between the facing ends thereof.

5. The method of claim 4 including the step of clamping the superposedfirst members together, following the step of closing the spacingbetween the facing ends of the second members.

6. A method of constructing electrical inductive apparatus having agapped magnetic core structure, comprising the steps of:

providing an electrical winding having an opening therein for receivinga winding leg of a magnetic core,

providing a plurality of F-shaped laminations having a back portion,first and second projecting portions disposed at one end and midpoint,respectively, of said back portion, and with the first portion extendingoutwardly from the back portion by a dimension which exceeds that of thesecond portion, stacking said F-shaped laminations to provide apreliminary rectangular structure having first and second yoke portionsformed by the back portions of the laminations, first and second outerleg portions formed by the first portions of the laminations, and anintermediate leg portion formed by said second portions of thelaminations having a gap therein formed between facing ends of saidsecond portions, said intermediate leg portion being composed of twosections, one on each side of said gap s and each section having aplurality of superposed laminations,

said stacking step spacing the first and second yoke portions such thatthe ends of the first portions are overlapped by a dimension whichprovides a gap in the intermediate leg portion sufficient to receive theelectrical winding, v placing the electrical winding in the gap of theintermediate leg portion, with its opening aligned with the facing endsof the intermediate leg portions, and moving the yoke portions closertogether to provide a final rectangular structure which includes anintermediate leg portion having a gap therein, said gap being disposedwithin the opening of the windmg. 7. The method of claim 6 wherein thestep of moving the yoke portions together is terminated before the endsof the first portions abut the back portions of the first and secondyoke portions.

8. The method of claim 6 including the step of clamping the superposedlaminations of each section of the intermediate leg portion prior to thestep of moving the yoke portions together.

9. The method of claim 8 including the step of clamping the laminationportions together which make up the yoke portions and outer legportions.

